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Additionally, because the location of the dithering patterns always stays the same relative to the display frame, it is less prone to jitter than error-diffusion methods, making it suitable for animations. Because the patterns are more repetitive than error-diffusion method, an image with ordered dithering compresses better.
Most printers overlap the black dots slightly, so there is not an exact one-to-one relationship to dot frequency (in dots per unit area) and lightness.Tone scale linearization may be applied to the source image to get the printed image to look correct.
The most straightforward way to remove the halftone patterns is the application of a low-pass filter either in spatial or frequency domain. A simple example is a Gaussian filter. It discards the high-frequency information which blurs the image and simultaneously reduces the halftone pattern.
The term dither was published in books on analog computation and hydraulically controlled guns shortly after World War II. [1] [2] [nb 1] Though he did not use the term dither, the concept of dithering to reduce quantization patterns was first applied by Lawrence G. Roberts [4] in his 1961 MIT master's thesis [5] and 1962 article. [6]
Floyd–Steinberg dithering is an image dithering algorithm first published in 1976 by Robert W. Floyd and Louis Steinberg. It is commonly used by image manipulation software. For example when converting an image from a Truecolor 24-bit PNG format into a GIF format, which is restricted to a maximum of 256 colors.
Traditional amplitude modulation halftone screening is based on a geometric and fixed spacing of dots, which vary in size depending on the tone color represented (for example, from 10 to 200 micrometres). The stochastic screening or FM screening instead uses a fixed size of dots (for example, about 25 micrometres) and a distribution density ...
Atkinson dithering is a variant of Floyd–Steinberg dithering designed by Bill Atkinson at Apple Computer, and used in the original Macintosh computer. Implementation [ edit ]
For example, a dot pattern that covers 30% of the image area on film, but covers 50% when printed, is said to show a total dot gain of 20%. However, with today's computer-to-plate imaging systems, which eliminates film completely, the measure of "film" is the original digital source "dot".